This thesis describes the design and development and some applications of an integrated stimulation and measurement system for postural control research based on virtual reality (VR) methods and force platform posturography. The system exposes test subjects to visual stimulation with immersive computer-generated environments and measures their responses to the stimulation using a force platform. Analysis is carried out on the measured stabilograms.

Our first experiments show that virtual environments affect balance and that they can be designed to cause desired effects, such as leaning in different directions, in test subjects. We investigated the efficacy of a head-mounted display and the CAVE display for visual stimulation by exposing test subjects to the same virtual environments using both displays. There were significant differences in the responses between the two displays. Next, we constructed an integrated VR posturography system in a laboratory at the Hearing Center of Tampere University Central Hospital and tested it on control subjects and patients with diagnosed balance disorders. Responses of control subjects and patients with Ménière's disease differed significantly and provided good discrimination between the two groups. Because the stabilograms are difficult to intepret, we applied pattern recognition methods to summarize the differences in them between the two groups.

The applications described in this thesis show that VR is a versatile and effective visual stimulation method for use in postural control research.

Many of the experimental setups used the same hardware to implement a sequence of balance tests. The combination of VR visual stimulation and posturography provided an easy way to quickly and comprehensively characterize a test subject's postural stability.